1. Field of the Invention
This invention relates to a zoom lens and an electronic imaging apparatus using this zoom lens.
2. Description of Related Art
In recent years, instead of silver-halide film cameras, digital cameras provided with solid-state image sensors, such as CCDs (charge coupled devices) and CMOSs (complementary metal-oxide semiconductors), have constituted the main current. Such digital cameras are available in various types ranging from a high-function type for business use to a popular compact type. Of these, the popular compact type of digital camera has come to require a slim design, in addition to a compact design, so that the camera can be easily put into the pocket of clothing or a bag and is handy to carry, in order to meet the need of a user who wants to readily enjoy photography. Consequently, for a zoom lens used in the popular compact type of digital camera, a compacter design is required and at the same time, it is also required to have satisfactory brightness, a high variable magnification ratio exceeding 3, and the property that a field angle in a diagonal direction is more than 70°.
Each of Japanese Patent Kokai Nos. 2004-318107 and 2002-365543 sets forth an optical system which is a zoom lens applicable to the popular compact type of digital camera and comprises, in order from the object side, a first lens unit with negative power, a second lens unit with positive power, a third lens unit with positive power, and a fourth lens unit.